1. Field of Invention
The present invention relates to user displays in portable detector units, and in particular, to displays for indicating the location of a detected hidden object.
2. Related Art
Portable sensors, including handheld detector units, that are used to locate hidden objects are generally well known. U.S. Pat. Nos. 4,099,118 and 4,464,622, which are incorporated herein by reference, disclose detector units (e.g., "stud sensors" and alternating current detectors) that identify a hidden object's position behind, for example, a wall. Some detectors identify the hidden object by measuring a capacitance change in one or more sensor elements within the detector unit as the user moves the unit across the wall over the hidden object. Such objects include wooden structural studs, pipes, and other metal and nonmetal objects such as wiring.
Other well-known handheld detector units contain sensor element and detecting circuit combinations that measure electromagnetic field changes. Some of these detector types identify, for example, wires carrying alternating current. Others of these detector types identify, for example, objects that effect a local magnetic field, such as masses of metal or gas lines.
FIG. 1 illustrates a typical application in which a user holds a detector unit 10 against wall 12. The user moves detector 10 transversely, as indicated by the arrows, to detect an object hidden from view behind wall 12, such as framing stud 14. Circuits within detector unit 10 display the sensed information on display 16.
Handheld detector units typically display their sensed indications using a visual display, such as display 16. Sensor visual displays include light-emitting diodes (LEDs) and liquid crystal displays (LCDs) in various configurations of one or more elements. For example, the National brand model number EZ380B (a Japanese manufactured product) includes a somewhat arrow-shaped LED display. Another detector sold under the name "Intellisensor," made by The Stanley Works in New Britain, Conn., uses a vertical LED display. In addition, copending and commonly assigned U.S. patent application Ser. No. 09/134,157, filed Aug. 14, 1998 and incorporated herein by reference, and copending commonly assigned U.S. patent application Ser. No. 08/694,955 (U.S. Pat. No. 5,917,314, issued Jun. 29, 1999), filed Aug. 8, 1996 and incorporated herein by reference, disclose several LCD and LED display configurations. Detector unit visual displays are typically designed to assist the detector user in determining some characteristic of a sensed object, such as an edge or center. Referring again to FIG. 1, for example, display 16 may indicate stud 14's edge 18, a center position 20 located between edge 18 and edge 22, both edges 18 and 22, or other representations of stud 14.
Handheld detector LED or LCD displays are typically mounted in the detector unit housing. Thus the display is displaced both laterally and in depth from the surface under which the detected object is located. Furthermore, users often operate handheld detectors at skewed angles and in unusual positions such as when searching for objects that are behind ceilings, floors, corners, etc. For example, in FIG. 1, if stud 14 is located behind a wall that is close to a large visual obstruction, such as a water heater tank, the user will have difficulty seeing display 16. Even if display 16 is visible, the skewed viewing angle requires the user to make a visual angular estimate of the hidden object's location behind the wall's surface, based on the display's position in the detector unit housing. What is desired, therefore, is a way to improve the way detector information is displayed to the user.